The present invention relates to underwater diving equipment and, more particularly, to devices for facilitating the equalization of pressure between the diver's middle and outer ear.
As shown in FIG. 1, the human ear is made up of three sections, commonly designated the outer ear, the middle ear and the inner ear. The outer ear includes the portion of the ear from the eardrum 10 outward to the ear opening. The inner ear includes the cochlea 12 and the three semi-circular canals 14. The middle ear is that portion of the ear between the eardrum 10 and the inner ear.
The middle ear is connected to the mouth cavity (not shown) through the eustachian tube 16, whose chief function is to equalize the pressure between the middle ear and the mouth cavity (typically the ambient pressure). Thus, under normal conditions, whenever the ambient pressure rises, the pressure in outer ear rises, as does the pressure in the mouth cavity. The rise in pressure in the mouth cavity brings about a concomitant rise in the middle ear through the eustachian tubes. The result is adequate pressure equalization between the outer and middle ear across the eardrum (see FIG. 2).
The pressure equalization is particularly important for divers since the ambient pressure changes dramatically and rapidly as the diver lowers himself beneath the water surface or rises toward the water surface.
The pressure equalization may be delayed or prevented when secretions block the eustachian tubes (see FIG. 3). This may be the case when the diver's eardrum is excited by low temperatures, water or pressure which brings about edema with its excessive secretion from the mucous membranes surrounding the middle ear and the eustachian tube. The edema furthermore narrows the eustachian tubes.
Furthermore, when diving the pressure on the outer ear increases almost instantaneously while the pressure in the middle ear increases at a lower rate, because of the narrowness of the eustachian tubes, which causes, for a short time, a relative under-pressurized condition in the middle ear. This under-pressure can stimulate the secretion of mucous and blood from the tissue surrounding the middle ear and eustachian tube and could lead to the blockage of the eustachian and the prevention of further pressure stabilization.
The result of a pressure differential between the outer and middle ear can vary from discomfort to great pain and could, in some cases, lead to the rupture of the eardrum.
Additionally, it is desirable to prevent the entry of cold water into the ear, which could result in loss of balance, stimulated ear mucous and blood secretions and bacterial infections.
To prevent the pressure equalization and related difficulties, it has been proposed to prevent entrance of water into the ear and to provide external tubes which functionally supplement the eustachian tubes and which serve to equalize the pressure across the eardrum.
U.S. Pat. No. 4,896,380 discloses a facemask which is equipped with a pair of tubes. Each tube features an earplug at its far end. Each of the earplugs can be plugged into the ear canal and air from the facemask is able to reach the outer ear through the tube in order to equalize the pressure across the eardrum. A disadvantage of such a system is that the air pressure from the mask is transferred directly to the outer ear without any delay or attenuation which could cause the user considerable discomfort. In addition, the earplugs tend to get dislodged from the ears during a dive, which leads to loss of air and discomfort. A further disadvantage is that a blockage of one of the tubes could create a significant pressure difference in the two ears which could greatly inconvenience the diver.
U.S. Pat. No. 2,488,235 also discloses an underwater facemask equipped with a pair of tubes. Each tube communicates at its far end with a substantially semi-spherical ear cup which covers the user's ear. The strap of the facemask serves to push the ear cups toward the user's ears. A disadvantage of such a system is that the strap securing the facemask to the face of the diver and the ear cups are essentially separate units so that the strap exerts inward pressure on the ear cups without relation to the ambient water pressure which destroys any chance of fine tuning the pressure on the user's ears, as described below. A further advantage is that the use of a pair of tubes makes it possible for one tube to get blocked which would create a pressure difference in the two ears with adverse consequences for the diver.
There is thus a widely recognized need for, and it would be highly advantageous to have, a simple and reliable device which will aid divers by equalizing the pressure between the outer and middle ear and between the two ears of the diver in a way which will minimize or eliminate discomfort.